Executive Summary : | In the last few years, significant research interest has grown over millimeter (mm-wave) wireless systems owing to their high data rate, low latency, and reliable communications. However, high energy consumption, path and penetration loss restrict the use of 5G and future generation (6G, 7G) systems in outdoor environments. Reconfigurable intelligent surfaces (RISs) have recently emerged as a promising solution to this problem since they can establish additional communication paths by modifying the electromagnetic (EM) wave propagation characteristics. RIS technology is also attractive in terms of spectral and energy efficiency. These structures can be easily integrated into buildings and other areas, thereby achieving a smart radio environment (SRE). Several internet of things (IOT) can greatly benefit from the concepts of SREs, such as smart cities, smart communication etc. An RIS is a periodic metasurface with inductive or capacitive elements located at sub-wavelength distance loaded with active components to control the phase and/or amplitude of the reflection response. By regulating the components using biasing circuitries, the RIS can be tuned either constructively to increase the overall signal amplitude in the direction of the intended receivers or destructively to avoid leaking signals to undesired receivers. However, a significant number of technology gaps are present in the existing RIS technology. Firstly, the earlier presented RIS models are discussed in light of communication network only; no accurate EM model is available for analyzing the RIS geometries. Secondly, a limited number of practical demonstration has been carried out with restricted EM operations (i.e. reflection, transmission) only. Further, no dedicated communication unit has been developed for remotely programming the RIS systems. Above all, the RIS concepts have only been explored in lower range of frequencies, and no 6G or future wireless network has been developed exploiting the RIS technology, to the best of our knowledge. Limited resources, complicacy in design models, and scarcity of measuring instruments restrict the in-depth exploration of RIS technology. In this project proposal, all the above limitations are planned to resolve with suitable solutions. Initially, the earlier reported RIS geometries will be studied and an accurate EM circuit model will be designed for the proposed RIS geometry. Based on the model analysis, RIS geometries will be numerically modeled in a simulation software, exhibiting electrically tunable reflection amplitude (between 0 and -30 dB), or/and reflection phase (ranging from +180 to -180 degree). The proposed RIS geometry will operate around 95 GHz covering 10% operating bandwidth with 40 degree angular stability. The structure will then be fabricated and experimentally demonstrated. Finally, a communication unit will be built to dynamically program the overall RIS system for its commercial deployment in 6G/7G wireless systems. |